Element with expansible relief

ABSTRACT

An element ( 10 ) comprises sealed cavities ( 24 ) arranged according to a regular pattern. Each cavity ( 24 ) contains a product such as a wax which changes in volume, in reversible fashion, when a given temperature threshold is crossed, together with an individual heating organ ( 26 ). The cavities ( 24 ) are separated from the front face ( 10   a ) of the element by a mobile or deformable organ ( 38 ). A separate piloting for each of the heating organs ( 26 ) makes it possible to make the relief of the front face ( 10   a ) of the element evolve in controlled fashion. Such an element can be used to re-transcribe, in relief, tactile (visually handicapped) or visual information.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority based on International PatentApplication No. PCT/FR01/01926, entitled “Element With Evolutive Relief”by Raymond Fournier, Alain Riwan and Jacques Beaupin, which claimspriority of French application no. 00 07928, filed on Jun. 21, 2001, andwhich was not published in English.”

TECHNICAL FIELD

[0002] The invention relates to an element with one front facepresenting an evolutive relief, enabling it in particular tore-transcribe tactile or visual information in relief.

[0003] The element relating to the invention can be used in manydomains. Among the possible applications, one can cite, in particular,the production of Braille reading systems for the visually handicappedor the production of computer interfaces such as elements able toreconstitute the texture of objects or materials, within the frameworkof electronic commerce. Mention can also be made of transparent screensin relief able to be superposed on normal visualisation screens.

STATE OF THE ART

[0004] As shown, in particular, by documents FR-A-2 577 998 and EP-A-0663 633, it is known how to use wax actuators to control various organs(valves, distributors, etc.) in household appliances such asrefrigerators, freezers, dish-washers or clothes-washers. These waxactuators are present in the form of a jack, in which the movement ofthe mobile shank forming a piston is controlled by the variation involume of a wax sealed in a hermetic cavity. This change in volume isdue to a change in state of the wax, generally between a solid state anda liquid state, produced by crossing a predetermined temperaturethreshold. The change in state of the wax is generally produced byheating the wax, to Make it pass from the solid state to the liquidstate. The phenomenon is reversible.

[0005] Waxes suitable for use in this type of actuator are sufficientlynumerous to allow the fusion point to be adjusted at will. By usingnormal waxes, the increase in volume produced by the change of phase isof the order of 10 to 15%. The use of special waxes even makes itpossible to achieve increases in volume exceeding 20%.

[0006] Wax actuators have the advantage of very low production costs.Furthermore, they can produce big changes for very significantdisplacements.

[0007] The essential disadvantages of present wax actuators relates totheir relatively long response time, due to their thermal inertia.

[0008] Moreover, elements are known with evolutive relief, mainly usedin Braille reading systems for the visually handicapped. In theseelements, magnetic or piezoelectric actuators are generally used,arranged according to a pattern, to make the relief of the front face ofthe element develop in function of the information to be transmitted.

[0009] These existing elements have the disadvantages of beingrelatively expensive and of being of limited dimensions. Furthermore,the use of magnetic or piezoelectric actuators provides them with lowresolution. In other terms, the texture of the relief obtained isrelatively rough. Finally, with these actuators one cannot envisage theproduction of transparent screens in relief able to re-transcribe visualinformation, associated with traditional visualisation screens.

DESCRIPTION OF THE INVENTION

[0010] The precise aim of the invention is an element with evolutiverelief without the disadvantages of existing elements and with anoriginal design allowing it, in particular, to be able to benefit fromlarge dimensions, an especially high resolution, and enabling theproduction of transparent elements usable on normal visualisationscreens, at very low cost.

[0011] According to the invention, this result is obtained by means ofan element with a front face with evolutive relief, said element beingcharacterised in that it comprises sealed cavities, distributedaccording to a regular pattern and filled with a product able to changevolume when a predetermined threshold temperature is crossed, adeformable or mobile organ separating each cavity of the front face,individual heating means for the product contained in each cavity, andcontrol means able to pilot all the individual heating means of theelement separately.

[0012] The layout in the element of a matrix of devices comparable tothe wax actuators used in prior art in household appliances and theseparate piloting of each of these devices makes it possible to obtainthe results announced. In particular, an element designed in this way isespecially low in cost, is not limited in size and implementstechnologies very suitable for miniaturisation and, consequently,enables the production of very high definition elements for representingtextured surfaces.

[0013] Moreover, the use of a transparent product and transparentmaterials makes it possible to produce an element in relief, alsotransparent. Such an element can be superposed on a traditionalvisualisation screen for re-transcribing visual information in relief.

[0014] Parallel to this latter application, the element according to theinvention can be applied, more classically, to transcription in reliefof tactile information. Thus it is possible to produce Braille readingsystems for the visually handicapped, computer interfaces, or elementscapable of reconstituting the texture of objects or materials forelectronic commerce applications.

[0015] In the preferred embodiments of the invention, the heating meansare heating organs piloted by an electric current. The control means arethus connected to these heating organs by electrical conductors with amatrix layout.

[0016] Depending on the case, the electrical conductors can either crossa rear wall, preferably rigid, of the element or be supported by asubstrate, preferably rigid, such as a printed circuit on which the rearface of the element is formed.

[0017] In a first embodiment according to the invention, the cavitiesare defined by perforations formed in a plate, preferably rigid.

[0018] In this case, the deformable or mobile organ comprises either apiston able to slide in each perforation of the front face side of theelement, or an elastic membrane covering the rigid plate of the frontface side of the element, in such a way as to close the perforationshermetically. In the former case, a recall means can be associated witheach piston, to bring it back automatically to rest position, when theproduct contained in the corresponding cavity has cooled.

[0019] In a second embodiment according to the invention, the cavitiesare defined integrally within an elastic membrane with one front faceforming the front face of the element.

[0020] Advantageously, in order to accelerate cooling of the productcontained in a given cavity after implementing the corresponding heatingmeans, forced cooling means are provided for this product, such as arefrigerating fluid circuit.

[0021] According to an advantageous development of the invention, atleast one temperature sensor is used to measure the overall temperature.The control means are then sensitive to a signal delivered by thissensor for overall adjustment of the piloting of the heating means,meaning in particular the idle current and the overall activationcurrent of the heating means when the latter are constituted by heatingorgans piloted by an electric current.

[0022] As a variant, a local temperature sensor can measure thetemperature of each means of heating. The control means are thensensitive to a signal delivered by each of the sensors for localadjustment of the piloting of each heating means, meaning in particularthe idle current and the individual activation current of each of theheating means, when the latter are constituted by heating organs pilotedby an electric current.

[0023] In another embodiment variant, the control means use themeasurement of the current crossing the heating organs and the voltageat the terminals of these organs to estimate their temperature and toadjust an idle current and an activation current for the heating organs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Now, as non-limiting examples, different embodiments of theinvention will be described, with reference to the attached drawings, inwhich:

[0025]FIG. 1 is a cross-section, on a large scale, showingdiagrammatically a part of an element in relief illustrating a firstembodiment of the invention;

[0026]FIG. 2 is a view comparable to FIG. 1, showing a variant of thefirst embodiment of the invention;

[0027]FIG. 3 is cross-section comparable to FIGS. 1 and 2, showing asecond embodiment of the invention; and

[0028]FIG. 4 shows diagrammatically the matrix control of the heatingorgans used in the elements of FIGS. 1 to 3.

DETAILED DESCRIPTION OF SEVERAL PREFERRED EMBODIMENTS ACCORDING TO THEINVENTION

[0029]FIG. 1 shows diagrammatically a part of an element with evolutivesuperficial relief according to a first embodiment according to theinvention. To make it easier to understand, the thickness of thiselement in panel form has deliberately been very accentuated in thefigure. In practice, this thickness is, for example, closely equal to 1or 2 mm.

[0030] The element 10 has a front face 10 a, with evolutive relief,intended to be turned outwards, and a back face 10 b.

[0031] The element 10 shown in FIG. 1 comprises a rigid plate 12, madefor example in metal or any other suitable material. The plate 12 shownin FIG. 1 is plane; however, a plate of different form (bulging, hollowetc.) can be used depending on the application envisaged, withoutextending beyond the framework of the invention.

[0032] Perforations 14 are made in the plate 12, following a regularpattern, so as to form a matrix of perforations in said plate. Thepattern formed by the matrix of perforations 14 can be a pattern withsquare, triangular or other shaped pitch, without extending beyond theframework of the invention.

[0033] The perforations 14 are generally all of the same dimension andhave, for example, although evidently non-limiting, a circularcross-section. All the perforations 14 open onto a front face and onto aback face of the plate 12. The front face of the plate 12 forms thefront face 10 a of the element 10.

[0034] The element 10 further comprises a rear rigid wall 20, appliedand fixed in sealed manner against the back face 18 of the plate 12. Inpractice, the rear wall 20 can be constituted, for example, either of aresin closing the corresponding extremities of the perforations 14, orof a film of a material such as those constituting integrated circuits,advantageously with high thermal conductivity. The wall 20 is fixed tothe plate 12 by any appropriate means ensuring the seal of theperforations 14 (gluing, etc.).

[0035] In the embodiment of the invention shown in FIG. 1, a mobileorgan such as a piston 22 is housed in sliding fashion in the part ofeach of the perforations 14 opening onto the front face 10 a. Moreprecisely, each of the mobile organs 22 hermetically closes thecorresponding perforation 14 of the front face side 10 a.

[0036] Each of the perforations 14 thus defines a cavity 24 internally,hermetically closed, between the rear wall 20 and the mobile organ 22.This cavity 24 is filled with a product capable of changing volume whena predetermined temperature threshold is crossed. In particular, thisproduct can be constituted by a wax which is in the solid state atambient temperature and in the liquid state when the temperature risesabove a predetermined temperature threshold, and whose volumeautomatically increases when it changes phase from the sold state to theliquid state, and vice versa. Such a wax is comparable to the waxesimplemented in existing wax actuators used in certain householdappliances. However, more generally, the product contained in each ofthe cavities 24 can be constituted by any other product with therequired characteristics, such as a polymer, a shape memory alloy, etc.

[0037] When the product contained in the cavities 24 is a wax, thechoice of the latter makes it possible to adjust at will the temperaturethreshold at which the volume change takes place, together with theamplitude of this volume change. This amplitude is generally comprisedbetween 10 and 15%, but in certain cases can exceed 20%.

[0038] In order to ensure that the threshold temperature for the productcontained in the cavities 24 is crossed, a heating means 26 for thisproduct is placed in each of said cavities. In the embodiment shown moreprecisely in FIG. 1, this heating means 26 is a heating organ of theresistive wire type, piloted by an electric current applied to theheating organ by electrical conductors 28. These electrical conductors28 cross the rigid rear wall 20 of the element 10. They form a matrixmaking it possible for each of the individual heating organs 26 to besupplied separately, from a control unit 30, as shown diagrammaticallyin FIG. 4.

[0039] When the element 10 is not being used, there is no electricalsupply to any of the heating organs 26. The product contained in thecavities 24 then returns to its original state corresponding, forexample, to its solid phase in the case of a wax. In these conditions,the volume of product contained in each of the cavities 24 is such thatthe extremities of the mobile organs turned towards the front face 10 aare flush with this face. In this initial state, the front face 10 athus has no relief.

[0040] When one or several heating organs 26 are supplied electricallyby the control unit 30, these organs 26 heat the product contained inthe corresponding cavities 24, in such a way that this product crossesthe temperature threshold at which it changes state. In the case wherethe product is a wax, it passes into the liquid phase. This change ofstate has the consequence of significantly increasing its volume. Thisresults in a displacement of the corresponding mobile organ(s) 22towards the front face 10 a of the element. The mobile organ(s) 22concerned then protrude beyond this front face 10 a, for a predetermineddistance (for example, about 200 microns), as shown in FIG. 1 for thesecond organ from the right.

[0041] The arrangement described thus makes it possible to make therelief of the front face 10 a of the element evolve at will, in order tore-transcribe some sort of information in relief on this face. Asalready noted, this information can, in particular, be used in tactilemanner by visually handicapped persons, for example for reading inBraille, for acting as a computer interface, or by sighted personswithin the framework of electronic commerce applications.

[0042] The information re-transcribed in relief on the front face 10 aof the element can also be of visual nature. In this case, the productand the different parts such as the plate 12, the mobile organs 22 andthe rear wall 20 can be produced in transparent materials. Thus atransparent screen with evolutive relief is produced, able to be placedover a traditional visualisation screen.

[0043] In order to improve the response time of the element 10, theindividual return of each of the mobile organs 22 to its original statecan be accelerated by associating a recall means to each of theseorgans, such as a compression spring 36 interposed between the oppositeshoulders 32 and 34 formed respectively in each of the perforations 14and on each of the mobile organs 22. For simplification, the spring 36has only been shown in the left-hand perforation 14 in FIG. 1.

[0044] Also, in order to reduce the response time of the element,advantageously one lowers the thermal inertia slowing the return of themobile organs 22 to their original state when the heating organs 26 areno longer supplied. Thus, the rear wall 20 is made in a material withhigh thermal conductivity, as mentioned above.

[0045] In order to further improve the evacuation of the heat producedby the heating organs 26, when they are no longer being supplied, forcedcooling means can be integrated with the rear wall 20, associatedindividually with each of the heating organs 26. These forced coolingmeans are, for example, by fluid circulation. They are then connected toa cooling system (not shown) outside the element.

[0046] Although the mobile organs 22 are shown in the form of steppedpistons in FIG. 1, these organs can also be constituted of cylindricalpistons of uniform cross-section, without extending beyond the frameworkof the invention.

[0047] In an embodiment variant shown in FIG. 2, the mobile organs 22are suppressed and replaced by a single elastic membrane 38, coveringthe whole of the front face of the plate 12. The elastic membrane 38 isthen fixed in sealed fashion onto the plate 12, for example by gluing,so as to close the perforations 14 hermetically. In this case, the frontface 10 a of the element 10 is constituted by the face of the elasticmembrane 38 turned outwards.

[0048] In this embodiment variant, the change in volume of the productcontained in the cavities 24 results in a deformation of the elasticmembrane 38 outwards from the element 10, in front of the concernedperforations 14, as shown for the second perforation from the right inFIG. 2.

[0049] The material constituting the membrane 38 is chosen so as to besufficiently elastic, or even super-elastic, to be able to return theproduct contained in the cavities 24 back to the initial position,during cooling.

[0050] This embodiment variant is preferable to the preceding variant,because of its implementation simplicity.

[0051] In a second embodiment according to the invention, shown in FIG.3, the cavities 24 containing the product able to change in volume whencrossing a predetermined temperature threshold are made directly in anelastic membrane 42. In this case, the cavities 24 do not open out ontothe front face of the elastic membrane 42, forming the front face 10 aof the element 10. Consequently, as in the embodiment variant of FIG. 2,each cavity 24 is separated from the front face 10 a of the element by adeformable organ, constituted in this case by a part of the membrane 42.

[0052] The back face of the elastic membrane 42 is fixed in sealedfashion, for example by gluing, onto a rigid substrate 46 on which theback face 10 b of the element 10 is formed. The rigid substrate 46carries, on its face turned towards the elastic membrane 42, heatingmeans 26 received individually in each of the cavities 24.Advantageously, these heating means 26 are constituted by heating organspiloted by an electric current. In this case, the electric current canin particular be directed separately to each of the individual heatingorgans 26 by electrical conductors 28 implanted directly in the rigidsubstrate 46. This can, for example, be in the form of a printedcircuit.

[0053] The heating organs 26 together with the electrical conductors 28are arranged in matrix fashion, in the form shown in FIG. 4, as in thecase of the first embodiment described and its variant.

[0054] In the embodiment of FIG. 3, the cavities 24 have anon-cylindrical shape, comparable to a bubble. This shape is determinedso as to produce as great a deformation as possible of the deformableorgans of the membrane 42, separating the cavities 24 from the frontface 44, during the change in volume of the product.

[0055] The embodiment shown in FIG. 3 is preferable to precedingembodiments, in that the production of the element is even simpler thanin the variant of FIG. 2.

[0056] In all embodiments, means can advantageously be envisaged tolimit temperature swings in the active cells constituted by the cavities24 filled with product on either side of the temperature thresholdcorresponding to the phase change of said product, taking hysteresisphenomena into account. These limitation means are aimed at ensuring thesystem with adequate dynamics, taking into account the fact thattemperature swings are very dependent on the ambient temperature and theoverall temperature of the complete system, which also depends on itsutilisation.

[0057] Thus the means for limiting temperature swings of the activecells comprise means for adjusting the temperature using the signalsdelivered by one or several temperature sensors.

[0058] According to a first possible arrangement, one or severaltemperature sensors 48 (FIG. 4) measure the overall temperature of theelement 10. The command unit 30 is then sensitive to the signalsdelivered by each temperature sensor 48 for global adjustment of thepiloting of the heating means 26. In the case where these heating meansare constituted by heating organs piloted by an electric current asdescribed above, the control unit 30 modulates the idle current and theactivation current sent to the heating organs, in function of theoverall temperature measured by the sensor(s) 48 integrated into theelement 10.

[0059] According to a second possible arrangement, a temperature sensor48′ (FIG. 4) is integrated locally into each of the cells 24, and inparticular into each of the heating means 26. The signals delivered bythe sensors 48′ are transmitted to the control unit 30 and the latteradjusts the temperature locally by adjusting the piloting of eachheating means 26 locally. In the case described where the heating means26 are heating organs piloted by an electric current, the control unit30 locally modulates the idle current and the activation current sent tothis heating organ.

[0060] In another embodiment variant (not shown) the temperature sensorsare suppressed and the temperature is deduced from measurement of thecurrent crossing the heating organ and from the voltage at the terminalsof this organ. On the base of this information, the control unit 30modulates the idle current and the activation current sent to theheating organs.

[0061] It should be noted that such means for temperature adjustment canadvantageously be associated with active cooling means such as thosedescribed above, so as to further improve the diffusion of heat towardsthe outside the element. Whatsoever the embodiment of the elementaccording to the invention, this can be produced at very low cost.Furthermore, the size of the element is not limited and it is possibleto produce screens in relief of large dimensions.

[0062] Furthermore, the activation temperature adjustment can beaccessible to the user, thus enabling this temperature to be adjusted infunction of the utilisation conditions.

[0063] Moreover, the technology proposed is very suitable forminiaturisation. In particular, the element can be produced bymicro-machining techniques. It is then possible to obtain very highdefinition for representation of textured surfaces.

[0064] Finally, as noted concerning the first embodiment described withreference to FIG. 1, the element according to the invention makes itpossible to produce transparent screens with evolutive relief able to besuperposed on traditional visualisation screens. This possibilityconcerns all the possible embodiments of the invention, on conditionthat the materials and the product used are transparent.

1. Element with a front face with evolutive relief, said elementcomprising individual means for modifying the relief of the front face,arranged according to a regular pattern and control means capable ofpiloting separately all the individual means for modification of therelief of the element, wherein the individual modification means of therelief comprise sealed cavities filled with a product able to changevolume when a predetermined temperature threshold is crossed, adeformable or mobile organ separating each cavity of the front face, andindividual heating means for the product contained in each cavity, wherethe heating means are heating organs piloted by an electric current andthe control means are connected to these heating organs by electricalconductors with a matrix layout.
 2. Element according to claim 1,wherein the electrical conductors cross a rear wall of the element. 3.Element according to claim 1, wherein the electrical conductors aresupported by a substrate on which a back face of the element is formed.4. Element according to claim 1, wherein the cavities are defined byperforations formed in a plate.
 5. Element according to claim 4, whereinthe deformable or mobile organ comprises a piston able to slide in eachperforation, on the side of the front face of the element, in such a wayas to close the perforations hermetically.
 6. Element according to claim5, wherein a recall means is associated with each piston, to return itautomatically to an idle position.
 7. Element according to claim 4,wherein the deformable or mobile organ comprises an elastic membranecovering said plate on the side of the front face of the element, so asto close the perforations hermetically.
 8. Element according to claim 1,wherein the cavities are integrally defined within an elastic membranewith one front face forming the front face of the element.
 9. Elementaccording to claim 1, wherein at least one temperature sensor measuresthe overall or local temperature of the element and the control meansare sensitive to a signal delivered by each sensor to adjust, overall orlocally, piloting of the heating means.
 10. Element according to claim9, wherein the control means adjust, overall or locally, an idle currentand an activation current for the heating organs.
 11. Element accordingto claim 1, wherein the control means use the measurement of the currentcrossing the heating organs and the voltage at the terminals of theseorgans to estimate their temperature and to adjust an idle current andan activation current for the heating organs.